1,389 research outputs found
Derivation of the superconducting gap equation for the noncentrosymmetric superconductor Li2Pt3B
We present here the mathematical background of our approach, presented in
Phys. Rev. B 86, 134526 (2012) regarding the gap function and symmetry for the
noncentrosymmetric (NCS) superconductor . As revealed by the
experiment, this NCS superconductor gives rise to line nodes in the
superconducting order parameter, which is responsible for many of its
experimental behaviors. Owing to the enhanced d-character of the relevant bands
that cross the Fermi level,the system gets weakly correlated. The nature and
symmetry of this nodal behavior is explained from a microscopic viewpoint. In
this article starting with an Hubbard model relevant for this NCS system by
considering the effect of the onsite Coulomb repulsion on the pairing potential
perturbatively, we extract the superconducting gap equation. Further analysis
of this equation predicts a wave gap function with line nodes as the
most promising candidate in the superconducting state.Comment: 7 pages, Proceeding versio
Ginzburg-Landau theory of noncentrosymmetric superconductors
The data of temperature dependent superfluid density in
LiPdB and LiPtB [Yuan {\it et al.}, \phrl97, 017006 (2006)]
show that a sudden change of the slope of occur at slightly lower
than the critical temperature. Motivated by this observation, we
microscopically derive the Ginzburg-Landau (GL) equations for
noncentrosymmetric superconductors with Rashba type spin orbit interaction.
Cooper pairing is assumed to occur between electrons only in the same spin
split band and pair scattering is allowed to occur between two spin split
bands. The GL theory of such a system predicts two transition temperatures, the
higher of which is the conventional critical temperature while the lower
one corresponds to the cross-over from a mixed singlet-triplet phase at
lower temperatures to only spin-singlet or spin-triplet (depending on the sign
of the interband scattering potential) phase at higher temperatures. As a
consequence, shows a kink at this cross-over temperature. We
attribute the temperature at which sudden change of slope occurs in the
observed to the temperature . This may also be associated with
the observed kink in the penetration depth data of CePtSi. We have also
estimated critical field near critical temperature.Comment: 7 pages, 1 figur
Relic density and PAMELA events in a heavy wino dark matter model with Sommerfeld effect
In a wino LSP scenario the annihilation cross section of winos
gravitationally bound in galaxies can be boosted by a Sommerfeld enhancement
factor which arises due to the ladder of exchanged W bosons between the initial
states. The boost factor obtained can be in the range S ~ 10^4 if the mass is
close to the resonance value of M ~ 4 TeV. In this paper we show that if one
takes into account the Sommerfeld enhancement in the relic abundance
calculation then the correct relic density is obtained for 4 TeV wino mass due
to the enhanced annihilation after their kinetic decoupling. At the same time
the Sommerfeld enhancement in the \chi \chi --> W^+ W^- annihilation channel is
sufficient to explain the positron flux seen in PAMELA data without
significantly exceeding the observed antiproton signal. We also show that (e^-
+ e^+) and gamma ray signals are broadly compatible with the Fermi-LAT
observations. In conclusion we show that a 4 TeV wino DM can explain the
positron and antiproton fluxes observed by PAMELA and at the same time give a
thermal relic abundance of CDM consistent with WMAP observations.Comment: 24 pages, 12 figures, 1 table; title corrected in arxiv metadat
Higgsino Dark Matter in Nonuniversal Gaugino Mass Models
We study two simple and well motivated nonuniversal gaugino mass models,
which predict higgsino dark matter. One can account for the observed dark
matter relic density along with the observed Higgs boson mass of ~ 125 GeV over
a large region of the parameter space of each model, corresponding to higgsino
mass of ~ 1 TeV. In each case this parameter region covers the gluino mass
range of 2-3 TeV, parts of which can be probed by the 14 TeV LHC experiments.
We study these model predictions for LHC in brief and for dark matter detection
experiments in greater detail.Comment: 35 pages, 11 figures, pdflatex, new references and a few relevant
decay branching ratios added in two tables. Version to appear in Phys Rev
PS-Sim: A Framework for Scalable Simulation of Participatory Sensing Data
Emergence of smartphone and the participatory sensing (PS) paradigm have
paved the way for a new variant of pervasive computing. In PS, human user
performs sensing tasks and generates notifications, typically in lieu of
incentives. These notifications are real-time, large-volume, and multi-modal,
which are eventually fused by the PS platform to generate a summary. One major
limitation with PS is the sparsity of notifications owing to lack of active
participation, thus inhibiting large scale real-life experiments for the
research community. On the flip side, research community always needs ground
truth to validate the efficacy of the proposed models and algorithms. Most of
the PS applications involve human mobility and report generation following
sensing of any event of interest in the adjacent environment. This work is an
attempt to study and empirically model human participation behavior and event
occurrence distributions through development of a location-sensitive data
simulation framework, called PS-Sim. From extensive experiments it has been
observed that the synthetic data generated by PS-Sim replicates real
participation and event occurrence behaviors in PS applications, which may be
considered for validation purpose in absence of the groundtruth. As a
proof-of-concept, we have used real-life dataset from a vehicular traffic
management application to train the models in PS-Sim and cross-validated the
simulated data with other parts of the same dataset.Comment: Published and Appeared in Proceedings of IEEE International
Conference on Smart Computing (SMARTCOMP-2018
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